Merge of plot_eval_form and plot_eval_func_call, syntactic forms are now defined in the env and can be stored as values.
Begin should return unspecified if there are no sub expressions to evaluate
GC reclamation of pairs will now correctly decr car and cdr, abstracted deconstructor into plot_value_decons
debug build will now include plot hash stats along with gc stats
Hash stats will now also print comp/get